Red Eared Slider & African Side Neck

Question
Why does my RES turtle seem to yawn when he is basking? We recently lost another one who did so frequently, especially the night before he died.  The pet store told me he probably had an URD. Is "yawning" normal?  Otherwise he is fine and eats voraciously!  He shares the tank with an African Side Neck, who also is a great hunter and eater, but is shy and stays in his cave and never basks.  We have the right UVB lighting and a heat lamp.

Answer
Yawning and stretching the neck out are classic signs of a respiratory infection--the yawning is because the turtle can't breathe.  Your other turtle probably died from untreated pneumonia.  You need to take this turtle to a reptile vet for diagnosis and treatment.  Turtles tend to hide symptoms, so once you see serious problems (not moving, not eating) it's often too late.  Don't put off getting treatment for your turtle.

The fact that you've had two turtles with problems indicates that something is wrong with how you're keeping them.  Tank size and water quality are very important.  You have two species that grow quite large, and the tank should also be large.  Just one RES adult really should be in a 100 gallon tank, and depending on the species of the side=neck, you should figure another 50-100 gallons for that turtle as well.  The other issue is that both these species can be aggressive, and at some point may begin fighting, so separating them may be a good idea.  Whatever you decide, a large tank(s) is absolutely necessary, and you also need a excellent quality filter (external canister) to keep the water quality pristine.

You should also recheck your water and basking temperatures, make sure you really do have a good UVB bulb (tubes need to be replaced every six months and MV bulbs yearly), and look at diet.  A varied diet is also important.  Pellets are fine as part of the diet, but it should also include fresh animal protein and greens.

I'm going to link some RES care information for you, as well as some general information on housing and water quality.  Please read it over carefully and make any changes necessary, but make sure you get your RES to a vet.  If you post back with the specific species of side-neck, I can provide information on that species as well.  

http://redearslider.com
http://www.austinsturtlepage.com/Care/caresheet-red_ear_slider.htm
http://www.austinsturtlepage.com/Care/care.htm
http://www.austinsturtlepage.com/Care/waterquality.htm
http://www.austinsturtlepage.com/Care/housing.htm